The record books for Greenland's climate were re-written on Tuesday, when the mercury hit 24.8°C (76.6°F) at Narsarsuaq, Greenland, on the southern coast. According to weather records researcher Maximiliano Herrera, this is the hottest temperature on record in Greenland for May, and is just 0.7°C (1.3°F) below the hottest temperature ever measured in Greenland. The previous May record was 22.4°C (72.3°F) at Kangerlussuaq (called Sondre Stormfjord in Danish) on May 31, 1991. The 25.2°C at Narsarsuaq on June 22, 1957 is the only June temperature measured in Greenland warmer than yesterday's 24.8°C reading. Wunderground's extremes page shows that the all-time warmest temperature record for Greenland is 25.5°C (77.9°F) set on July 26, 1990. The exceptional warmth this week was caused by the combination of an intense ridge of high pressure and a local foehn wind, said the Danish Meteorological Institute. The unusual May heat has extended to Scotland, which had its hottest May temperature on record on May 25 at Achnagart: 29.3°C (85°F). Greenland's Narsarsuaq has seen a string of 3 consecutive days over 70°F this week--the 3rd, 7th, and 12th warmest days there since record keeping began in 1941. The ridge of high pressure responsible is expected to stay in place several more days, bringing additional 70° days over Southern Greenland. The warm May temperatures could be setting the stage for a big Greenland melt season this summer--the International Research Institute for Climate and Society (IRI) is predicting a 50 - 60% that the southern 2/3 of Greenland will experience above-average temperatures this summer. They forecast just a 10 - 15% chance of below-average temperatures.

Figure 1. Difference between the number of melt days in 2011 and the average number of melt days during the period 1979 - 2010. Large sections of the island experienced twenty more days with melting conditions than average. Image credit: Arctic Report Card

Why Greenland is importantIf the massive icecap on Greenland were to melt, global sea level would rise 7 meters (23 ft). Temperatures in Greenland are predicted to rise 3°C by 2100, to levels similar to those present during that warm period 120,000 years ago. During that period, roughly half of the Greenland ice sheet melted, increasing sea level by 2.2 - 3.4 meters (7.2 - 11.2 ft.) However, the 2007 IPCC report expects melting of the Greenland ice sheet to occur over about a 1,000 year period, delaying much of the expected sea level rise for many centuries. While Greenland's ice isn't going to be melting completely and catastrophically flooding low-lying areas of the earth in the next few decades (sea level is only rising about 3 mm per year or 1.2 inches per decade at present), the risk later this century needs to be taken seriously. Higher sea levels will cause increased erosion, salt water intrusion, and storm surge damage in coastal areas, in addition to a loss of barrier formations such as islands, sand bars, and reefs that would normally protect coastal zones from battering by waves and wind. Additionally, coastal zones are sites of incredible economic and agricultural activity, which would also be negatively affected by higher sea levels. Currently, melting ice from Greenland is thought to cause about 0.7 mm/year of global sea level rise, which is about 20 - 25% of the global total, according to an international research group led by the GFZ German Research Centre for Geosciences, in an article published the latest issue of Earth and Planetary Science Letters, 1 June 2012. In 2007, the IPCC estimated that Greenland ice melt was responsible for only 10 - 15% of the total global sea level rise. Ice loss in Greenland is accelerating, and if current ice loss trends continue for the next ten years, Greenland's contribution to sea level rise will double to 1.4 mm/yr by 2022. The increased ice loss in Greenland is being driven by a combination of warmer air temperatures, warmer ocean temperatures, and loss of Arctic sea ice. Ocean temperatures surrounding Southern Greenland have increased by 1 - 2°C since 1990 (figure at right.)Figure 2. Monthly unsmoothed values of the total mass (in gigatons, Gt), of the Greenland ice sheet from the GRACE satellites. On the horizontal axis, each year begins on 1 January. Each small + symbol is a monthly value. Between 2003 - 2009, Greenland lost an average of 250 gigatons of ice per year. In 2011, the loss was 70% greater than that. Image credit: Arctic Report Card

Update on the 2011 Greenland melt seasonAccording to the 2011 Arctic Report Card, it was another very warm year in Greenland in 2011, which led to substantial melting of the ice. Here are some of the highlights from the report:

1) The area and duration of melting at the surface of the Greenland ice sheet in summer 2011 were the third highest since 1979.

2) Increased surface melting and below average summer snowfall in recent years has made the icecap steadily darker. In 2011, the icecap had the lowest reflectivity (albedo) of any year since satellite measurements of reflectivity began in 2000.

3) The area of glaciers that empty into the sea continued to decrease, though at less than half the rate of the previous 10 years.

4) Total ice sheet mass loss in 2011 was 70% larger than the 2003 - 2009 average annual loss rate of -250 gigatons per year. According to satellite gravity data obtained since 2002, ice sheet mass loss is accelerating.

Beryl headed out to sea

The center of Tropical Depression Beryl is close to the ocean again, and the storm has strengthened slightly in response. Beryl's heavy rain show will be focused on Eastern North Carolina today, where widespread rain amounts of 2 - 4 inches can be expected. Beryl's heaviest rains fell over Lafayette County, Florida, on Monday and Tuesday, where 12.65" was measured as of 6:30 am EDT Tuesday near Midway. Beryl spawned a single tornado on both Monday and Tuesday; these twisters did only minor damage. There is a slight chance the storm could produce another weak tornado today over North Carolina. The storm is being blamed for one death--a swimmer that drowned in rough surf in Daytona Beach, Florida. Another swimmer is missing from Folly Beach, South Carolina. All things considered, Beryl was just the sort of tropical storm the Southeast U.S. needed--strong enough to bring the heavy rains needed to alleviate the severe to exceptional drought conditions over the region, but not so strong as to cause major damage and loss of life. The main bummer was that Beryl hit during the Memorial Day holiday weekend, costing the tourism industry tens of millions of dollars in lost business. With Beryl caught in a trough of low pressure and accelerating to the northeast, the storm should transition to an extratropical storm later today.

Figure 1. True-color MODIS satellite image of Beryl taken at 2:25 pm EDT May 29, 2012 by NASA's Aqua satellite. At the time, Beryl was a tropical depression with winds of 30 mph.

Figure 2. Estimated rainfall from Beryl over the past seven days from NOAA/AHPS.

Beryl dumping heavy rains; all-time May heat records set in MI, OH

Tropical Depression Beryl continues to bring heavy rains to Northern Florida and Southern Georgia, but has begun to move northeast, and will be spreading heavy rains over coastal South Carolina today and North Carolina on Wednesday. Rains of 5 - 8 inches have been common over Northern Florida. These rains have caused numerous problems with street flooding, but no serious damage. The heaviest rains from Beryl so far have been to the southwest of the center, over Lafayette County, Florida, where 12.65" was measured as of 6:30 am EDT Tuesday near Midway. Beryl spawned one tornado on Monday, near Florida's St. Lucie Medical Center. The twister damaged two roofs and brought down trees and power lines. One swimmer is missing from Folly Beach, South Carolina, and a 19 year old man is missing and presumed drowned from swimming in rough surf in Daytona Beach, Florida. Before becoming a tropical cyclone, Beryl produced heavy rainfall over Cuba, especially Sancti Spíritus Province, where meteorologists reported more than 20 in (510 mm) of precipitation. The rains caused mudslides and flash floods, destroying 47 houses and damaging 1,109 more. Two people died attempting to cross flooded rivers in Cuba.

Figure 1. True-color MODIS satellite image of Beryl taken at 12:05 pm EDT May 28, 2012 by NASA's Terra satellite. At the time, Beryl was a tropical depression with winds of 35 mph.

Forecast for BerylBeryl will continue to spin and dump copious rains as it treks through Southern Georgia today, and coastal South Carolina and North Carolina on Wednesday. These rains will generally not be heavy enough to cause damaging flooding, since the region is under moderate to severe drought. When Beryl pops off the coast near the North Carolina/South Carolina border on Wednesday, wind shear will be low enough and ocean temperatures warm enough to allow re-intensification to a tropical storm. However, tropical-storm-force winds will probably be limited to the right-front side, over the ocean, and the coast of North Carolina will see winds no greater than 35 mph.

July-like heat wave brings hottest May temperatures on record to Michigan, OhioA strong high pressure system anchored over the central U.S. brought more record-smashing May heat to much of the country on Monday. The heat was most notable in Southern Lower Michigan and Northern Ohio, where Detroit (95°F), Flint (93°), Cleveland (92°F), and Toledo, Ohio (96°) tied or set records for their hottest temperature ever recorded in May. On Saturday, at least nine airports in the Midwest had their hottest May day on record, and 58 out of 456 U.S. airports set daily high temperature records. On Sunday, at least sixteen airports in the Midwest had their hottest May day on record, and 68 out of 456 U.S. airports set daily high temperature records. Eight airports in the Western U.S. set daily coldest temperature records on Sunday; no airports have set an all-time coldest May temperature record in the U.S. this month. Temperatures 5 - 10°F above average are expected over portions of New England today, but the May 2012 heat wave is pretty much over for the U.S.

Beryl makes landfall, weakens to a tropical depression

Tropical Storm Beryl lumbered ashore near Jacksonville Beach, Florida at 12:10 am this Memorial Day as an intensifying tropical storm with 70 mph winds. Beryl is only the second named storm to hit on a Memorial Day weekend in the U.S. (the three-day weekend was established in 1971.) The other was Subtropical Storm Alpha of 1972, which followed a path almost identical to Beryl's and made landfall as a 60 mph subtropical storm. Beryl's 70 mph winds at landfall make it the strongest landfalling May tropical cyclone since the May 29, 1908 hurricane, which had 75 mph winds when it brought tropical storm-force winds to the Outer Banks of North Carolina.

Figure 1. True-color MODIS satellite image of Beryl taken at 2:35 pm EDT May 27, 2012 by NASA's Aqua satellite. At the time, Beryl was a tropical storm with winds of 65 mph.

Damage from Beryl has been mostly minor, with reports of street flooding, trees down, one house with a roof torn off, and power outages to 25,000 people in the Jacksonville, Florida area. One swimmer is missing from Folly Beach, South Carolina, and lifeguards performed dozens of rescues along the Southeast U.S. coast over the weekend due to rip currents generated by Beryl's rough surf. A tornado warning was issued near 10:30 am EDT this morning for the region near the coast to the east of Jacksonville, and Beryl's spiral bands could produce rotating thunderstorms that will trigger more tornado warnings today. A few of the top winds generated by Beryl over the past day:

Forecast for BerylBeryl has weakened to a tropical depression, but will continue to spin and dump copious rains as it slowly treks through northern Florida, Southern Georgia, and coastal South Carolina Monday and Tuesday. Radar-estimated rainfall amounts as of Monday morning were generally 1 - 4 inches in Northern Florida and Southern Georgia, with a few regions of 4+ inches. Flooding due to heavy rains is probably not a huge concern with this storm, since the Southeast U.S. coast is under moderate to exceptional drought. The 4 - 8 inches of rain expected from Beryl will provide significant drought relief in Florida and Georgia, which are suffering rainfall deficits of 9 - 12 inches (Figure 3.) When Beryl pops off the coast of South Carolina or North Carolina on Wednesday, the storm will probably be moving fast enough that it won't have time to generate enough rain to cause serious flooding problems in those states.

Figure 3. Much of the Southeast U.S. needs 9 - 12 inches of rain (red colors) to bust the current drought. A drought is defined as "busted" when the Palmer Drought Severity Index (PDSI) goes higher than -0.5. Image credit: NOAA.

July-like heat wave continues over much of the U.S.A strong high pressure system anchored over the central U.S. brought more record-smashing May heat to much of the country on Sunday. The heat was most notable in Indiana, where both South Bend (97°F) and Fort Wayne (96°F) set records for their hottest temperature ever recorded in May. Rockford, Illinois (99°) and Chicago (97°) both had their hottest temperature on record so early in the year. On Saturday, at least nine airports in the Midwest had their hottest May day on record, and 58 out of 456 U.S. airports set daily high temperature records. A compensating sharp dip in the jet stream allowed three airports in the Western U.S. to set daily coldest temperature records on Saturday. Numerous all-time May heat records will be threatened in the Great Lakes and Ohio Valley today, where temperatures 15 - 20°F above average are expected.

Beryl a little stronger, closes in on Southeast U.S. coast

The beach-going weather this Memorial Day weekend will deteriorate rapidly this afternoon along the Southeast U.S. coast near the Florida/Georgia border, where Subtropical Storm Beryl is steadily closing in. A hurricane hunter aircraft found top surface winds near 60 mph in heavy thunderstorms to the northeast of Beryl's center at 9:15 am EDT this morning; top winds in the region to the southwest of the center were a little weaker, near 55 mph. This region is now approaching the coast of northern Florida. Winds at the Buoy 41012, 46 miles ENE of St. Augustine and to the southeast of Beryl's center, hit 38 mph gusting to 49 mph, at 11 am EDT this morning. Wave heights at the buoy were 12 feet, and Beryl is driving heavy surf that is generating dangerous rip currents along a large section of the Southeast U.S. coast. On Saturday, at least 32 people were rescued by lifeguards at Tybee Island, Georgia due to strong rip currents generated by Beryl's crashing surf.

Figure 1. True-color MODIS satellite image of Beryl taken at 12:20 pm EDT May 26, 2012 by NASA's Aqua satellite. At the time, Beryl was a subtropical storm with winds of 45 mph.

Forecast for BerylBeryl is still a subtropical storm, as evidenced by its large, cloud-free center, but the storm is steadily building a large amount of heavy thunderstorms near the center this morning, as the storm traverses the core of the Gulf Stream. The warm 27 - 28°C (81 - 83°F) waters of the Gulf Stream are helping warm and moisten the atmosphere near Beryl's core, and it is possible that Beryl will become a tropical storm before landfall late Sunday night. As I explain in my Subtropical Storm Tutorial, the fact that the storm has not been able to generate a tight inner core with heavy thunderstorms near the center will limit its intensification potential, and we need not be concerned about rapid intensification of Beryl while it is still subtropical.The clockwise flow of air around an extremely intense ridge of high pressure that is bringing record heat to the Midwest this weekend is currently driving Beryl to the west. As Beryl approaches the coast tonight, the storm will move off of the warmest Gulf Stream waters into waters that are cooler (25°, 77°F), and with lower total heat content. A portion of the storm's circulation will also be over land, and these two factors will limit the storm's potential to strengthen. Beryl is also struggling against a large amount of dry that surrounds the storm, due to the presence of an upper-level trough of low pressure. The 11 am Sunday wind probability advisory from NHC gave Beryl just an 6% chance of becoming a hurricane before landfall. Flooding due to heavy rains is probably not a huge concern with this storm, particularly since the Southeast U.S. coast is under moderate to extreme drought. The 3 - 6 inches of rain expected from Beryl will not be enough to bust the drought, since the Southeast U.S. is generally suffering a rainfall deficit of 9 - 12 inches (Figure 4.) Heavy rains from Beryl will begin affecting coastal Georgia and Northern Florida near 3 pm Sunday.

Figure 3. Predicted rainfall from Beryl, as taken from the 06 UTC May 27, 2012 run of the HWRF model. A large area of 4 - 8 inches of rain (dark green colors) is predicted for the drought-stricken areas of Northern Florida and Southern Georgia. Image credit: Morris Bender, NOAA/GFDL.

Figure 4. Much of the Southeast U.S. needs 9 - 12 inches of rain (red colors) to bust the current drought. A drought is defined as "busted" when the Palmer Drought Severity Index (PDSI) goes higher than -0.5. As seen from the HWRF precipitation forecast in Figure 3, most of the drought relief from Beryl will occur near the coast, and the most needy areas (purple colors in Figure 3) are expected to get little rainfall. Image credit: NOAA.

Scorching May heat wave hits much of the U.S.; severe weather expected in the MidwestAn exceptionally strong high pressure system anchored over the central U.S. is bringing record-smashing May heat to much of the country this Memorial Day weekend. Dozens of daily high temperature records fell on Saturday, including several all-time records for the month of May. Vichy-Rolla, Missouri hit 98°F, beating its all-time May heat record of 95° set on May 15, 1899. Columbus, Georgia hit 97°F, tying the record hottest May day on record. Saturday's high of 100°F in Tallahassee was the second highest May temperature since record keeping began in 1892. Pensacola's 98°F on Saturday was its second highest May temperature since record keeping began in 1879 (the record May temperature in both cities is 102°F, set on May 27, 1953.) Nashville, Tennessee hit 95°F on Saturday, just 1° shy of their all-time May heat record. That record could fall today, and numerous all-time May heat records will be threatened in the Midwest, Great Lakes, and Tennessee Valley. As is often the case when one portion of the country is experiencing record heat, the other half is seeing unusually cool conditions, due to a large kink in the jet stream. Billings, Montana received 1.3" of snow Saturday, and Great Falls had received 2.3" as of 6 am this morning. The dividing line between the warm conditions in the Eastern U.S. and cool conditions to the west lies over Nebraska and Kansas today, and NOAA's Storm Prediction Center (SPC) has placed portions of these states in their "Moderate Risk" area for severe weather--the second highest level of alert.

Subtropical Storm Beryl forms

The second named storm of this unusually fast-starting 2012 Atlantic hurricane season is here. Subtropical Storm Beryl formed Friday night, a few hundred miles east of the South Carolina coast, from an area of disturbed weather that had moved from the Western Caribbean northeastward. Beryl's formation marks the first time since the hurricane season of 1908 that two Atlantic named storms have formed so early in the year. The only other year with two storms so early in the year was 1887. Records of tropical cyclones in the Atlantic extend back to 1851.

Figure 1. Morning satellite image of Beryl.

The clockwise flow of air around an extremely intense ridge of high pressure that is bringing record heat to the Midwest this weekend is currently driving Beryl to the southwest, and this motion is likely continue until Beryl is very close to the Georgia/Northern Florida coast on Sunday night. As I explain in my Subtropical Storm Tutorial, a subtropical storm typically has a large, cloud free center of circulation, with very heavy thunderstorm activity in a band removed at least 100 miles from the center. The difference between a subtropical storm and a tropical storm is not that important as far as the winds they can generate, but tropical storms generate more rain. A key difference between tropical and subtropical storms is that tropical systems have the potential to quickly grow into hurricanes, while subtropical storms do not. Thus, we need not be concerned about Beryl intensifying to hurricane strength while it is still subtropical. If the storm manages to build a large amount of heavy thunderstorms near its center, these thunderstorms should be able to add enough heat and moisture to the atmosphere to turn Beryl into a tropical storm. This process will be aided as Beryl passes over the warmest waters of the Gulf Stream Saturday night and Sunday morning. But as Beryl makes its likely transition to a tropical storm on Sunday afternoon and evening as it approaches the coast, the storm will move off of the warmest Gulf Stream waters into waters that are cooler (25°, 77°F), and with with lower total heat content. This will limit the storm's potential to strengthen. The 11 am Saturday wind probability advisory from NHC gave Beryl just an 8% chance of becoming a hurricane. There is a lot of dry air surrounding Beryl, thanks to an upper-level low pressure system aloft, and this will keep rainfall amounts much lower that what we would expect if Beryl was a tropical storm. Thus, flooding due to heavy rains is probably not a huge concern with this storm, particularly since the Southeast U.S. coast is under moderate to extreme drought. The 2 - 4 inches of rain expected from Beryl will not be enough to bust the drought, since the Southeast U.S. is generally suffering a rainfall deficit of 8 - 12 inches (since October 1.) Heavy rains from Beryl are not likely to begin affecting coastal South Carolina, Georgia, and Northern Florida until Sunday.

Figure 2. Moderate to exceptional drought is currently gripping the Southeast U.S.; Beryl's rains would be welcome. Image credit: U.S. Department of Agriculture.

Bud hits Mexico and dissipatesHurricane Bud hit Mexico as a tropical depression early this morning, and has now dissipated, thanks to dry air, wind shear, and interaction with Mexico's mountainous terrain. As Bud approached Mexico on Friday, it brought tropical storm-force winds and heavy rains to the coast. Winds at Manzanillo peaked at 41 mph, with a gust to 55 mph, Friday afternoon. Thursday night at 11 pm EDT, Bud peaked at Category 3 status, with 115 mph winds, becoming the earliest Category 3 hurricane on record so early in the year in the Eastern Pacific. There are no reports of deaths or damage from Bud so far, and with only another inch or so of rain expected from the storm, Mexico appears to have escaped serious damage.

Figure 3. True-color satellite image of Hurricane Bud taken by NASA's Terra satellite at 1:15 pm EDT May 25, 2012. At the time, Bud was a Category 1 hurricane with 85 mph winds. Image credit: NASA.

Bud the strongest Eastern Pacific hurricane so early in the year; 94L may develop

Category 2 Hurricane Bud is weakening, but still presents a formidable rainfall threat as it continues north-northeast towards an expected landfall between Manzanillo and Puerto Vallarta, Mexico late Friday night. Thursday night at 11 pm EDT, Bud peaked at Category 3 status, with 115 mph winds, becoming the earliest Category 3 hurricane on record in the Eastern Pacific. Recent Satellite loops show that Bud has weakened, though. The eye has disappeared, and the cloud pattern has shrunk and appears squashed, due to an increase in dry air, wind shear, and cooler sea surface temperatures affecting the storm. These hostile conditions should continue to weaken Bud to a Category 1 hurricane or strong tropical storm by the time of landfall. Bud is projected to cross the coast in a rugged, relatively unpopulated area, so wind and storm surge damage will probably be light to moderate. Heavy rain will cover a much wider area, and will be the main threat from Bud. The coast where Bud is headed towards is very mountainous, and numerous flash floods and dangerous mudslides will affect the region, probably including the cities of Manzanillo and Puerto Vallarta. I don't think Puerto Vallarta will see much in the way of wind or storm surge damage, since it is in a well-protected location and will probably be on the weak (left-front) side of the hurricane. Manzanillo is at higher risk, since it will probably be on the stronger right-front side of the hurricane.

Figure 1. True-color satellite image of Hurricane Bud taken at 12:25 pm EDT May 24, 2012. At the time, Bud was a Category 2 hurricane with 110 mph winds. Image credit: NASA.

A record May for the Eastern Pacific hurricane seasonBud is the strongest Eastern Pacific hurricane on record for so early in the year, and is tied with Hurricane Alma of 2002 (115 mph winds) as the second strongest May hurricane on record in the Eastern Pacific. Only Hurricane Adolph of 2001 (145 mph winds) was stronger. Also, Bud's appearance on May 21 marked the earliest date since record keeping began in 1949 for formation of the season's second named storm. The previous record was set in 1984, when the second named storm formed on May 29. Hurricanes are uncommon in the Eastern Pacific in May; there have been just twelve since record keeping began in 1949--an average of one May hurricane every five years. If Bud ends up making landfall in Mexico as a hurricane, it would be only the second Eastern Pacific May hurricane on record to hit Mexico. The other was Hurricane Agatha of May 24, 1971, which hit the same stretch of coast that Bud is threatening. Agatha made landfall as a Category 2 hurricane about 45 mi (75 km) from Zihuatanejo, Mexico. Ocean temperatures this year in the region where Aletta and Bud formed are only slightly above average, so the large-scale atmospheric patterns are probably more to blame for this year's exceptionally early start to hurricane season in the Eastern Pacific.

Figure 2. Morning satellite image of Invest 94L.

Invest 94L off the Georgia coast could develop this weekendAn area of disturbed weather (Invest 94L) a few hundred miles east of the Georgia coast is headed northeast at about 15 mph. The disturbance has not become more organized over the past day, due to very high wind shear of 40 - 55 knots. However, the latest SHIPS model forecast predicts that wind shear will drop to the moderate range, 10 - 20 knots, on Saturday and Sunday. Most of our reliable models predict that 94L could organize into a subtropical or tropical depression or storm on Saturday or Sunday off the coast of Georgia/South Carolina. NHC is giving 94L a 70% chance of developing into a tropical or subtropical depression by Sunday morning. A ridge of high pressure is expected to build in over the weekend off the East Coast, which will force 94L to the west back towards the coast, and heavy rains from 94L are likely to begin affecting coastal South Carolina, Georgia, and Northern Florida on Saturday and Sunday. There is a lot of dry, continental air on the west side of 94L, so the rainfall amounts from the storm will be limited unless until the center makes landfall. If these rains do materialize, they would be welcome, considering the moderate to severe drought conditions in the area.

NOAA predicts a near-normal Atlantic hurricane season

NOAA forecasts a near-normal Atlantic hurricane season in 2012, in their May 24 outlook. They give a 50% chance of a near-normal season, a 25% chance of an above-normal season, and a 25% chance of a below-normal season. They predict a 70% chance that there will be 9 - 15 named storms, 4 - 8 hurricanes, and 1 - 3 major hurricanes, with an Accumulated Cyclone Energy (ACE) 65% - 140% of the median. If we take the midpoint of these numbers, NOAA is calling for 12 named storms, 6 hurricanes, 2 major hurricanes, and an ACE index 102% of normal. This is very close to the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2011 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 153% of the median. Only five seasons since 1995 have not been above normal--including four El Niño years (1997, 2002, 2006, and 2009), and the neutral 2007 season.

Figure 1. The strongest Atlantic hurricane of 2011, Ophelia, as seen at 1:40 pm EDT October 1, 2011. At the time, Ophelia was a Category 3 hurricane with 120 mph winds. At 11 pm that night, Ophelia peaked at Category 4 strength with 140 mph winds. Image credit: NASA.

The forecasters cited the following main factors that will influence the coming season:

1) Near-average sea surface temperatures (SSTs) are expected in the hurricane Main Development Region (MDR), from the Caribbean to the coast of Africa between between 10°N and 20°N. SSTs in the MDR during April were near-average, and are expected to remain so during hurricane season, based on current observations, climatology, and long-range model forecasts.

2) We are in an active period of hurricane activity that began in 1995, thanks to a natural decades-long cycle in hurricane activity called the Atlantic Multidecadal Oscillation (AMO): "During 1995-2010, some key aspects of the tropical multi-decadal signal within the MDR have included reduced vertical wind shear and weaker easterly trade winds, below-average sea-level pressure, a configuration of the African easterly jet that is more conducive to hurricane development from tropical cloud systems (aka Easterly waves) moving off the African coast, and warmer than average SSTs."

3) An El Niño event may occur this year: "Another climate factor known to significantly impact Atlantic hurricane activity is the El Niño-Southern Oscillation (ENSO.) The three phases of ENSO are El Niño, La Niña, and ENSO-Neutral. El Niño events tend to suppress Atlantic hurricane activity, while La Niña events tend to enhance it (Gray 1984). If El Niño fails to develop, the probability of an above-normal Atlantic hurricane season will be higher and the actual seasonal activity will likely be toward the upper end of our predicted ranges." There is currently of lot of uncertainty whether or not an El Niño event will develop in time for the August - September - October peak of hurricane season--the latest NOAA El Niño discussion is giving a 41% chance of an El Niño event during hurricane season, and a 48% chance of neutral conditions.

4) NOAA is increasingly using output from ultra-long range runs of the computer forecast models we rely on to make day-to-day weather forecasts, for their seasonal hurricane forecasts: "The outlook also takes into account dynamical model predictions from the NOAA Climate Forecast System (CFS), the European Centre for Medium Range Weather Forecasting (ECMWF), the United Kingdom Meteorology (UKMET) office, and the EUROpean Seasonal to Inter-annual Prediction (EUROSIP) ensemble. These models show large spreads in the ENSO forecasts for ASO, ranging from ENSO-Neutral to a moderate-strength El Niño episode. As a result, their forecasts for the Atlantic hurricane season also show a considerable spread, ranging from slightly above normal to slightly below normal."

How accurate are the NOAA seasonal hurricane forecasts?A talk presented by NHC's Eric Blake at the 2010 29th Annual AMS Conference on Hurricanes and Tropical Meteorology studied the accuracy of NOAA's late May seasonal Atlantic hurricane forecasts, using the mid-point of the range given for the number of named storms, hurricanes, intense hurricanes, and ACE index. Over the past twelve years, a forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Using another way to measure skill, the Mean Squared Error, May NOAA forecasts for named storms, hurricanes, and intense hurricanes had a skill of between 5% and 21% over a climatology forecast. Not surprisingly, NOAA's August forecasts were much better than the May forecasts, and did significantly better than a climatology forecast.

Figure 2. Mean absolute error for the May and August NOAA seasonal hurricane forecasts (1999 - 2009 for May, 1998 - 2009 for August), and for forecasts made using climatology from the past five years. A forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

94L may develop this weekend; Hurricane Bud intensifies near Mexico

An area of disturbed weather (Invest 94L) over South Florida, Cuba, the Bahamas, and the Western Caribbean is bringing gusty winds heavy rains to the region, and is headed north-northeast along the east coast of Florida. Miami is under an areal flood watch today for rains of 1 - 3 inches, and rains in excess of one inch have already fallen over Key Largo today. The disturbance is generating some impressive winds this morning along the Southeast Florida coast--Fowey Rocks recorded sustained southeast winds of 33 mph at 10am EDT, and Molasses Reef on Key Largo had 31 mph sustained winds. The disturbance is under a very high 40 - 50 knots of wind shear, according that the latest SHIPS model analysis, making development very unlikely today. As 94L slides north-northeast along the coast on Friday and Saturday, wind shear is expected to decrease, and several of our reliable models predict that 94L could organize into a subtropical depression on Saturday or Sunday off the coast of North Carolina/South Carolina. NHC is giving 94L a 20% chance of developing by Saturday morning. A ridge of high pressure is expected to build in over the weekend off the East Coast, which will force 94L to the southwest back towards the coast. Heavy rains from 94L are likely to begin affecting coastal South Carolina, Georgia, and Northern Florida on Saturday and Sunday. If these rains do materialize, they would be welcome, considering the moderate to severe drought conditions in the area.

Hurricane Bud heads towards MexicoHurricane Bud finally took advantage of its favorable environment of low wind shear and warm ocean temperatures and became a Category 2 hurricane this morning. Recent satellite loops show a well-organized storm with a prominent eye, cold eyewall cloud tops, and good low-level spiral banding. It is possible that Bud could attain Category 3 status later today. An Air Force hurricane hunter aircraft will investigate Bud this afternoon to gauge Bud's strength. Hurricanes are uncommon in the Eastern Pacific in May; there have been just twelve since record keeping began in 1949--an average of one May hurricane every five years. The earliest Eastern Pacific hurricane was Hurricane Alma of 1990, which became a hurricane on May 15. There have been only two major Category 3 or stronger May hurricanes. Here is a list of the twelve May hurricanes in the Eastern Pacific:

Forecast for BudBud will continue towards the coast of Mexico the next two days, pulled northwards by a trough of low pressure moving across the U.S. This trough will lift out and a ridge of high pressure will build in its place, and most of the computer models predict Bud will stall just offshore--or get pulled apart so that its low level center stays offshore, and its mid-level center moves inland. NHC is currently basing its track forecast on the ECMWF and GFS models, which were the two best performing models in both 2010 and 2011. An outer spiral band of Bud is already bringing a few heavy rain showers to the coast of Mexico near Manzanillo, and rains will increase in intensity on Friday and Saturday. The hurricane is expected to encounter more hostile condition--dry air, cooler SSTs, and higher wind shear--that will weaken the storm on Friday and Saturday. This should decrease the winds enough so that heavy rain will be the main threat from Bud. The coast where Bud is headed towards is very mountainous, and flash floods and dangerous mudslides will be a concern there. The region was not under drought conditions as of the end of April, but a number of wildfires are currently burning in the area, so Bud's rains may also do some good, by extinguishing these fires.

Invest 94L bringing heavy rains; Bud finally strengthening

An area of disturbed weather in the Western Caribbean is bringing heavy rains to the Cayman Islands and Central Cuba. This disturbance was designated Invest 94L by NHC this morning. The disturbance is under a high 30 - 40 knots wind shear, according that the latest SHIPS model analysis. This high shear is not expected to diminish over the next few days, and 94L will have a tough time developing in the face of such high wind shear. The disturbance should move north-northeast across Cuba today and Thursday, bringing heavy rains to Cuba, South Florida, and the Bahamas. Miami received a hefty 9.7 inches of rain on Tuesday, a record for the date, and moisture streaming northeastwards from 94L today and Thursday will contribute to the widespread street flooding the city is experiencing. An areal flood watch has been posted for Miami, and an additional 1 - 2 inches of rain are expected today.

Figure 1. Morning satellite image of Invest 94L.

Tropical Storm Bud continues as a minimal-strength 40 mph storm this morning in the Eastern Pacific, ignoring seemingly favorable conditions for strengthening. However, recent satellite loops show a more organized appearance to the storm, with increased low-level spiral banding, so Bud may finally be responding to the favorable conditions for intensification--low wind shear of 5 - 10 knots and SSTs of 28 - 29°C. On Thursday and Friday, wind shear will rise to the moderate level, SSTs will cool, and total heat content of the waters will decline, which may limit Bud's potential to reach hurricane strength. Almost all of our reliable models are now forecasting that the trough of low pressure pulling Bud towards the coast of Mexico will not be strong enough to bring Bud ashore, and the storm could linger near the coast for several days. The potentially still exists for Bud to deluge the coast near Manzanillo with very heavy rains capable of triggering dangerous flash floods and mudslides on Friday and Saturday, but the delayed intensification of Bud is making this prospect look less likely.

Tropical Storm Bud intensified into a 40 mph storm this morning in the Eastern Pacific, off the coast of Mexico, and poses a significant flooding threat to the country late this week. The storm has been slow to organize due to its large size, as seen on satellite loops. But with favorable SSTs of 29 - 30°C and light to moderate wind shear in the 5 - 15 knots range expected along its path, Bud should steadily organize today and Wednesday, and become Hurricane Bud by Thursday. A trough of low pressure is expected to swing north of the storm late this week, turning Bud to the north towards the Mexican coast between Manzanillo and Acapulco. However, the trough of low pressure may not be strong enough to bring Bud ashore, and the storm could linger near the coast for several days, potentially deluging the coast with very heavy rains capable of triggering dangerous flash floods and mudslides, beginning on Friday.

Figure 1. Morning satellite image of Bud.

Record earliest date for formation of the season's second named stormBud is the second named storm to form in the Eastern Pacific in 2012--Tropical Storm Aletta, which formed on May 15, was the first. Bud's appearance on May 21 marks the earliest date since record keeping began in 1949 for formation of the season's second named storm. The previous record was set in 1984, when the second named storm formed on May 29. Only two other years have had two named storms in May in the Eastern Pacific--2007 and 1956, which both had the second named storm of the year form on May 30. If Bud ends up making landfall in Mexico as a hurricane, it would be only the second Eastern Pacific May hurricane on record to hit Mexico. The other was Hurricane Agatha of May 24,1971, which hit the same stretch of coast that Bud is threatening. Agatha made landfall as a Category 2 hurricane about 45 mi (75 km) from Zihuatanejo, Mexico. The village of Playa Azul was hard hit by the storm, with up to half of the village's homes destroyed. Ocean temperatures this year in the region where Aletta and Bud formed are only slightly above average, so the large scale atmospheric patterns are probably more to blame for this year's exceptionally early start to hurricane season in the Eastern Pacific.

Alberto headed out to seaTropical Depression Alberto is racing northeastwards out to sea, and has been substantially weakened by very high wind shear of 50 knots and passage over cool ocean waters of 24°C (75°F). Alberto will not trouble any land areas, and does not have long to live before being completely dismantled by the high wind shear.

One-year anniversary of the Joplin, Missouri EF-5 tornadoMay 22 marks the 1-year year anniversary of the deadly Joplin Missouri tornado. The massive EF-5 tornado with winds in excess of 200 mph mowed a 14-mile path of destruction up to one mile wide across the southern portion of the city. The tornado killed 161 people--the highest death toll from a U.S. tornado since 1947, and the seventh deadliest tornado in U.S. history. The tornado did $3 billion in damage, making it the most expensive tornado in world history. The death toll from the tornado undoubtedly would have been higher had the National Weather Service not issued a tornado warning a full 24 minutes in advance of the tornado. This is nearly double the average tornado warning lead time of thirteen minutes.

LinksThe most remarkable audio I've ever heard of people surviving a direct hit by a violent tornado was posted to Youtube by someone who took shelter in the walk-in storage refrigerator at a gas station during the Joplin tornado. There isn't much video.

Video 1. Video of the Joplin, Missouri tornado of May 22, 2011, entering the southwest side of town. Filmed by TornadoVideos.net Basehunters team Colt Forney, Isaac Pato, Kevin Rolfs, and Scott Peake.

Alberto headed away from land; TD 2-E a concern for Mexico

Tropical Storm Alberto continues to struggle against strong upper level winds out of the west-southwest that are creating a very high 40 knots of wind shear over the storm. These winds are driving dry, continental air into Alberto, keeping its heavy thunderstorm activity quite limited. While the storm is being helped by the fact it is crossing the warm 27°C (81°F) waters of Gulf Stream today, this is not enough to offset the high wind shear. Small storms like Alberto are highly vulnerable to wind shear, and you can see all the dry air surrounding the storm, which the shear is driving into its core, on water vapor satellite loops. Alberto has begun an eastwards motion away from the coast, and will accelerate to the northeast later today and Tuesday as a trough of low pressure pulls it out to sea. Alberto has likely seen its peak intensity, and will not trouble any land areas. The storm brought up to an inch of rain to the coast near Savannah, Georgia on Sunday.

Figure 1. True-color visible satellite image of Alberto taken by the Aqua satellite at 2:30 pm EDT Sunday May 20, 2012. At the time, Alberto had maximum sustained winds of 45 mph. Image credit: NASA.

Eastern Pacific TD 2-E may become a dangerous hurricane for MexicoA more significant storm is newly-formed Tropical Depression 2-E in the Eastern Pacific, off the coast of Mexico. The depression is taking its time getting organized today due to its large size, as seen on satellite loops. But with favorable SSTs of 29 - 30°C and light to moderate wind shear in the 5 - 15 knot range expected along its path, TD 2-E should steadily organize on Tuesday and Wednesday, and become Hurricane Bud by Thursday. A trough of low pressure is expected to swing north of the storm late this week, turning TD 2-E to the north to a landfall between Manzanillo and Acapulco, Mexico on Friday. This storm has the potential to be a dangerous hurricane for the Mexican coast.

Spectacular annular eclipse of the sun on SundayOn Sunday, sky-watchers along the U.S. West Coast and in Asia were treated to a rare annular eclipse of the sun, where the moon blocked out all but a thin ring of light around the sun. Our wunderphotos gallery has fantastic collection of some great eclipse photos people took. Dr. Cliff Mass' blog has a nice satellite sequence showing the shadow of the eclipse affecting the U.S.

Alberto weakens, brings light rains to Georgia and South Carolina

Tropical Storm Alberto continues to move slowly to the west-southwest off the coast of South Carolina, and is bringing light rains to the coasts northern Georgia and southern South Carolina. Recent radar and satellite loops show that Alberto has weakened late this morning, and has lost most of its heavy thunderstorms. Upper level winds out of the west-southwest are creating a moderate 15 - 20 knots of wind shear over Alberto, and these winds are driving dry air into the storm, which has caused it to deteriorate. The dry air impinging on Alberto can be seen in water vapor satellite loops. Yesterday, Alberto was over the warm 81°F (27°C) water of the Gulf Stream, but today, the storm has moved west of the Gulf Stream, and is now centered over cooler waters of 79°F (26°C). This gives the storm a lot less energy to power it, and as Alberto drifts farther to the west-southwest today, ocean temperatures will get even cooler. A hurricane hunter aircraft is scheduled to visit Alberto this afternoon.

Figure 1. Late morning visible satellite image of Alberto.

Forecast for AlbertoSporadic rain showers from Alberto are likely to affect the Georgia and South Carolina coasts today, and the coasts of North Carolina and South Carolina on Monday. The heaviest rains and tropical storm-force winds should remain offshore, but even if Alberto did make landfall, the storm is too small to cause major flooding problems, particularly since the coast is under moderate to severe drought. Alberto's rains will be generally less than an inch over land areas, which will not be plentiful enough to cause significant drought relief. Wind shear is expected to increase to the high range, 30 - 40 knots, tonight through Monday, which should be able to rapidly disrupt a storm as small as Alberto. Steering currents are weak, and Alberto will wander off the coast of South Carolina through Monday morning, before getting caught up by a trough of low pressure on Monday night which should lift the storm out to the northeast. NHC is giving Alberto a less than 5% chance of reaching hurricane strength. Alberto should cause little or no damage to the coast, except perhaps for some coastal erosion due to high waves.

Figure 2. Late morning total rainfall image of Alberto from the Charleston, SC radar. Alberto's rains have been less than one inch along the coast, and most of the rain has fallen offshore.

Alberto in historical contextAlberto is earliest-forming tropical storm in the Atlantic Basin since Ana in 2003, which formed on April 21. Alberto is one of only three Atlantic tropical storms to form in May in the past 31 years. The others were Tropical Storm Arthur of 2008, and Tropical Storm Arlene of 1981. There was also a subtropical storm, Andrea, that formed in May of 2007. Formation of an early season tropical storm from an old frontal boundary, like occurred with Alberto, is not a harbinger of an active hurricane season--it's more of a random occurrence. Early season storms that form in the Caribbean, though, often signal that a busy hurricane season may occur.

Tropical Storm Alberto forms off the South Carolina coast

The first named storm of the 2012 Atlantic hurricane season is here. Tropical Storm Alberto formed this afternoon off the coast of South Carolina--a little going-away present for outgoing NHC director Bill Read, who retires on June 1! Alberto has the potential to hit North Carolina as early as Monday, but since the storm is so small, it would only affect a small area of the coast with high winds and heavy rain. Upper level winds out of the southwest are creating a moderate 15 - 20 knots of wind shear over Alberto, and the storm is over the warm waters of Gulf Stream, which are 81°F (27°C), just above the 26°C threshold usually needed to sustain a tropical storm. The system is tangled up with an upper level trough of low pressure, which is pumping cold, dry air into the storm, slowing development. The dry air impinging on Alberto from the southwest can be seen in water vapor satellite loops. Heavy rain showers from Alberto are located about 50 miles offshore of the coast of South Carolina, as seen on Wilmington radar. At times today, 93L has had a cloud-free center resembling an eye on radar, but this was not a true eye.

Forecast for AlbertoRain showers from Alberto are likely to move onshore between Charleston and Wilmington Saturday night and Sunday, bringing 1 - 3 inches of rain to portions of the coast. The storm is too small to cause major flooding problems, particularly since the coast is under moderate to severe drought. Alberto's rains will not be plentiful enough to cause significant drought relief, except perhaps over a small region near the coast, where (and if) the storm makes landfall. Wind shear is expected to remain in the moderate range, 15 - 20 knots, through Monday, which is low enough to allow some slow development. Since the storm is very small, it is highly vulnerable to even a modest increase in wind shear or dry air, which could rapidly disrupt it. Steering currents are weak, and Alberto will wander off the coast of South Carolina through Sunday, before getting caught up by a trough of low pressure on Monday which should lift it out to the northeast. The moderate wind shear and dry air are likely to keep Alberto below hurricane strength. NHC is giving Alberto a 5 - 10% chance of reaching hurricane strength before dissipating on Thursday as it scoots northeast out to sea.

Alberto in historical contextAlberto is earliest-forming tropical storm in the Atlantic Basin since Ana in 2003, which formed on April 21. Alberto is one of only three Atlantic tropical storms to form in May in the past 31 years. The others were Tropical Storm Arthur of 2008, and Tropical Storm Arlene of 1981. There was also a subtropical storm, Andrea, that formed in May of 2007. Formation of an early season tropical storm from an old frontal boundary, like occurred with Alberto, is not a harbinger of an active hurricane season--it's more of a random occurrence. Early season storms that form in the Caribbean, though, often signal that a busy hurricane season may occur.

Disturbance 93L off South Carolina coast could become a tropical storm

A hybrid low pressure system with both tropical and extratropical characteristics has formed in the waters off the coast of South Carolina, about 120 miles southeast of Myrtle Beach--a little going-away present for outgoing NHC director Bill Read, who retires on June 1! Residents along the South Carolina and North Carolina coast should pay attention to 93L, as it has the potential to strengthen into a tropical storm and hit the coast on Sunday or Monday, with North Carolina at highest risk. NHC designated this system Invest 93L Saturday morning. Wind shear is a moderate 20 knots over 93L, and the storm is over the warm waters of Gulf Stream, which are 81°F (27°C), just above the 26°C threshold usually needed for a tropical storm to form. The system is tangled up with an upper level trough of low pressure, which is pumping cold, dry air into the storm, inhibiting development. Wind shear is expected to remain in the moderate range, 15 - 20 knots, through Monday, which is low enough that 93L has a decent chance of developing into the Atlantic's first tropical depression. Since 93L is very small, it is highly vulnerable to even a modest increase in wind shear or dry air, which could rapidly disrupt it. Conversely, the storm's small size and favorable positioning over the warm waters of the Gulf Stream mean it is also capable of suddenly organizing, and it would not be surprise to see 93L become Tropical Storm Alberto by Sunday. NHC is giving 92L a 50% chance of developing into a tropical depression or tropical storm by Monday. Since 93L is so small, the computer models are having trouble resolving it, and we don't have very good forecasts of the storm right now. Steering currents are weak, and I expect 93L will wander off the coast of South Carolina through Sunday, before getting caught up by a trough of low pressure on Monday which should lift it out to the northeast. Heavy rain showers from 93L are located about 50 miles offshore of the coast of South Carolina, as seen on Wilmington radar. These showers will probably move onshore between Charleston and Wilmington Saturday night and Sunday, bringing 1 - 3 inches of rain to portions of the coast. At times today, 93L has had a cloud-free center resembling an eye on radar, but this was not a true eye, and winds are probably near 35 - 40 mph in the heaviest rain squalls near the center.

April 2012: Earth's 5th warmest on record

April 2012 was the globe's 5th warmest April on record, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC). NASA rated April 2012 as the 4th warmest April on record. April 2012 global land temperatures were the 2nd warmest on record, and the Northern Hemisphere land surface temperature was 1.74°C (3.13°F) above the 20th century average, marking the warmest April since records began in 1880. Global ocean temperatures were the 11th warmest on record, and April 2012 was the 427th consecutive month with ocean temperatures warmer than the 20th century average. The last time the ocean temperatures were below average was September 1976. The increase in global temperatures relative to average compared to March 2012 (16th warmest March on record) was due, in part, to warming waters in the Eastern Pacific, due to the La Niña event that ended in April. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were 6th or 4th warmest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). April temperatures in the stratosphere were the 1st to 4th coldest on record. We expect cold temperatures there due to the greenhouse effect and to destruction of ozone due to CFC pollution. Northern Hemisphere snow cover during April was 4th smallest in the 46-year record. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of April in his April 2012 Global Weather Extremes Summary. Notably, national heat records (for warmest April temperature on record) occurred in the United States (a tie), Germany, Austria, Poland, Belarus, Lithuania, Moldova, Hungry, Croatia, Ukraine, and Slovakia as well as the cities of Moscow and Munich.

Figure 1. Departure of temperature from average for April 2012. The most notable extremes were the warmth observed across Russia, the United States, Alaska, and parts of the Middle East and eastern Europe. There were no land areas with large-scale cold conditions of note. Image credit: National Climatic Data Center (NCDC) .

La Niña officially endsAccording to NOAA's Climate Prediction Center (CPC), La Niña conditions are no longer present in the equatorial Pacific, where sea surface temperatures were approximately average as of May 13. The threshold for a La Niña is for these temperatures to be 0.5°C below average or cooler. CPC forecasts that neutral conditions will persist though the summer, with a 41% chance of an El Niño event developing in time for the August - September - October peak of hurricane season. El Niño conditions tend to decrease Atlantic hurricane activity, by increasing wind shear over the tropical Atlantic.

Figure 2. Arctic sea ice extent in 2012 (blue line) compared to the average (thick grey line.) The record low year of 2007 (dashed green line) is also shown. Arctic sea ice was near average during April, but has fallen well below average during the first half of May. Image credit: National Snow and Ice Data Center (NSIDC).

April Arctic sea ice extent near averageArctic sea ice extent was near average in April 2012, the 17th lowest (18th greatest) extent in the 35-year satellite record, according to the National Snow and Ice Data Center (NSIDC). This was the largest April Arctic sea ice extent since 2001. However, ice in the Arctic is increasingly young, thin ice, which will make it easy for this year's ice to melt away to near-record low levels this summer, if warmer than average weather occurs in the Arctic.

Figure 2. Mt. St. Helens in Washington State erupting on May 18, 1980. Image credit: USGS.

Video 1. In Grand Isle, Louisiana last week, a large waterspout came ashore as an EF-1 tornado. The tornado ripped the roof off of the house across the street from this videographer, who should have taken shelter instead of filming the destruction. There's one 4-letter word in the video. Thanks go to Andrew Freedman of Climate Central for posting this.

Have a great weekend, everyone! I'll be back Sunday or Monday with a new post.

The Hockey Stick and the Climate Wars: a book review

No climate scientist has been subject to more attacks on their science and character than Penn State's Michael Mann, originator of the famed "hockey stick" graph of Earth's temperature history. Dr. Mann has an excellent new book called "The Hockey Stick and the Climate Wars: Dispatches from the Front Lines" that takes the reader on a fascinating journey to the front lines the high-stakes battles between climate scientists and their detractors. It's a must-read for every serious student of Earth's climate. Along the way, you'll learn about tree rings, the IPCC process, the fossil fuel industry's savvy PR campaigns to discredit climate change science, and get an insider's view of the notorious stolen emails of "climategate."

For those unfamiliar with the "hockey stick", the shape of the graph showing Earth's temperature has a long, relatively flat portion representing the period 1000 AD - 1800 AD--the shaft of the hockey stick--followed by a sharp upward rise that began in the late 1800s and continues to this day--the blade of the hockey stick. When Dr. Mann first published the hockey stick graph in papers he wrote in 1998 and 1999, it quickly became a central icon in the climate change debate. As he writes in "The Hockey Stick and the Climate Wars," the hockey stick graph "told an easily understood story with a simple picture: that a sharp and highly unusual rise in atmospheric warming was occurring on Earth." Contrarians bent on discrediting the science of climate change have fiercely attacked the hockey stick, attempting to portray it as the key piece of evidence upon which all of climate change science depends (which is not correct, since many different data sets unrelated to the tree ring studies under attack show a hockey stick-like shape.) The contrarians have adopted "the Serengeti strategy" towards Dr. Mann--"a tried-and-true tactic of the climate change denial campaign...isolate individual scientists just as predators on the Serengeti Plain of Africa hunt their prey: picking off vulnerable individuals from the rest of the herd."

The history of the hockey stickThe book starts with some interesting background on Dr. Mann's career. He got into climate science by accident--while working on his Ph.D. in physics at Yale, funding got tight, and he elected to switch to the Department of Geology and Geophysics, where funding to perform research on natural climate cycles was available. In the mid-1990s, while working on his Ph.D., he helped discover the decades-long natural cycle of alternating warm and cool ocean temperatures in the Atlantic Ocean thought to be responsible for the active hurricane period that began in 1995. He gave the phenomenon the now widely-used name, the Atlantic Multidecadal Oscillation (AMO), during an impromptu interview with science writer Dick Kerr. After receiving his Ph.D. in 1996, Dr. Mann moved on into using statistical methods to study past climate, as gleaned from tree ring studies. He takes the reader on a 5-page college-level discussion of the main technique used, Principal Component Analysis (PCA), and shows how his famed "hockey stick" graph came about. It's one of the best descriptions I've seen on how PCA works (though it will be too technical for some.) His inaugural PCA work showing that the 1990s were likely the warmest decade in at least the past 600 years was published in 1998. Since the paper coincidentally happened to be published on Earth Day during the warmest year in Earth's history, the paper received a huge amount of media attention. His follow-up 1999 paper went further, suggesting that the 1990s were the warmest decade in the past 1,000 years, and 1998 was the warmest year. Dr. Mann was appointed as one of the lead authors of the 2001 Intergovernmental Panel on Climate Change (IPCC) report, the massive United Nations summary of climate change science that comes out every six years. We learn some interesting details about the approval process for the 2001 IPCC report, like the fact for two days, the scientists haggled with the Saudi Arabian delegation about one word in the Summary for Policy Makers. The IPCC report's summary requires unanimous approval by all nations, and the Saudis objected to the language that said, "the balance of evidence suggests an appreciable human influence on climate." They debated 30 different alternatives before finally settling on the language, "the balance of evidence suggests a discernible human influence on climate."

Figure 1. The hockey stick graph as it appeared in the IPCC Third Assessment Report WG1 (2001) summary, Figure 2.20, Northern Hemisphere temperature reconstruction. Tree rings, corals, ice cores, and historical records are shown in blue, and instrumental data in red, from AD 1000 to 1999. The grey shaded region indicates the uncertainty in the annual temperature estimates (there is a 95% certainty that the temperature for any given year lies in the gray shaded region.) The thick black line is a smoothed version which highlights the long-term variations. A similar version of this graph appeared in Dr. Mann's original 1999 paper. Climate scientist Dr. Jerry Mahlman was responsible for giving this graph the nickname, the "hockey stick".

The battle beginsThe majority of the book focuses on the battles over the hockey stick that ensued in 1998, as soon as Dr. Mann published his research. He writes: For more than a decade, the scientific community, in its effort to communicate the threat of climate change, has had to fight against the headwind of this industry-funded disinformation effort. The collective battles are what I term the "Climate wars". The battle raged furiously through 2006, when an extensive review of the hockey stick was performed by the National Academy of Sciences (NAS)--an organization founded in 1863 by Abraham Lincoln to "investigate, examine, experiment, and report upon any subject of science" for the purpose of informing government policy. The NAS reaffirmed the validity of the hockey stick, concluding: "based on the analyses presented in the original papers by Mann et al. and this new supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium." Dr. Mann writes, "One might think that this would have put an end to the accusations once and for all. But one would be wrong."

In November 2009, a few weeks before the December international climate summit in Copenhagen, the RealClimate.org website that Dr. Mann contributes to was hacked into, and a file with emails stolen from the University of East Anglia's Climatic Research Unit (CRU) was posted. Dr. Mann explains in detail how these "climategate" emails were taken out context and distorted to appear scandalous by "a massive public relations campaign conducted by major players in the climate change denial movement." To illustrate, he gives the example of Isaac Newton's writings, which can easily be taken out context and distorted to give the impression that he was guilty of "conspiring to avoid public scrutiny," "insulting dissenting scientists," "manipulation of evidence," "knowingly publishing scientific fraud," "suppression of evidence," "abusing the peer review system," and "insulting critics." In the end, no evidence of scientific misconduct was found by any of the five independent reviews of the affair, conducted by the UK Parliament, a CRU commission led by eminent geoscientist Lord Oxburgh, Penn State University, the National Science Foundation Office of the Inspector General, and the University of East Anglia. As a result of "climategate", nothing at all changed in the peer-reviewed scientific literature on climate change. It was a phony scandal.

A fierce advocate of good scienceAs I read the book, I was impressed by Dr. Mann's tremendous passion for science and knowledge that comes through. He loves figuring out how things work, and stands in fierce opposition to shoddy science and anti-science political attacks. I had the opportunity to sit down over a beer and talk with him at a recent conference, and he had little interest in talking politics. He'd much rather talk about science, and we had a great discussion about hurricanes--he's published several papers that use statistical techniques to estimate how many tropical storms we missed counting in the Atlantic before the advent of satellites. He frequently talks about how science works and the importance of following the scientific method in his book: "The scientific process--left to operate freely--is inherently self-correcting, even if the gears may at times turn more slowly than we would like...Scientists must be allowed to follow the path along which their intellectual inquiries take them, even if their findings and views might appear inconvenient to outside special interests." In the end, Dr. Mann is "cautiously optimistic" that humanity can meet the challenge of climate change, but acknowledges that climate scientists are in a "street fight" against well-funded climate change disinformers bent on obscuring the science.

Conclusion: five stars out of fiveThe Hockey Stick and the Climate Wars: Dispatches from the Front Lines is a must-read for every serious student of climate change science, and gets my highest rating: five stars out of five. The book is $17.78 at Amazon.com. True to its title, the book has spawned its own mini-war in the ratings section of Amazon, where readers either loved it or hated it--75% of the reviews were 4 or 5 stars, while 21% were 1 star reviews. Only 4% of the readers gave it a mediocre 2 or 3 star rating. Some of the 1 star reviews are no doubt there because “Watt’s Up With That,” one of the most prominent climate science confusion sites, put up a post calling on readers to attack Mann’s book and to attack positive reviews.

An interview with Dr. Mann about his book, "The Hockey Stick and the Climate Wars", appeared on Andy Revkin's Dot Earth blog in the New York Times on May 3.

My favorite climate science blog is realclimate.org, which Dr. Mann co-founded. You can see one of the latest challenges to the hockey stick answered in a May 11 post discussing tree ring records from Siberia.

The first Eastern Pacific tropical storm of the 2012 hurricane season is Tropical Storm Aletta, located about 650 mi south-southwest of Manzanillo Mexico. Aletta was named at 03 UTC May 15, right at the official May 15 beginning of the Eastern Pacific hurricane season. The storm is headed west-northwest away from Mexico, and will not trouble any land areas. It is unusual to get a tropical storm forming this early in the year in the Eastern Pacific; since record keeping began in 1949, there have only been two that have formed by May 15--Hurricane Alma of 1990, and an unnamed 1996 storm. Aletta will not live for long--the storm is headed towards a region with high wind shear and cooler waters that should be able to destroy it late this week.

Figure 1. Morning satellite photo of Tropical Storm Aletta.

Earth's longest tropical storm-free period in at least 70 yearsThe formation of Aletta ends a 41-day streak without a tropical storm anywhere in the world. According to the UK Met Office, the 41-day period storm-less period is the longest span Earth has gone without a tropical storm in at least 70 years. The last time there were as many as 38 consecutive storm-less days was in 1944. Prior to Aletta, the last tropical storm on the planet was Tropical Storm Daphne in the South Pacific, which dissipated 06 UTC April 3, 2012. April is usually is the quietest month globally for tropical cyclones. The long storm-less period comes in the midst of a very quiet two-year period of global tropical cyclone activity. According to Dr. Ryan Maue, who specializes in tracking global tropical cyclone activity, 2010 and 2011 saw a total of 146 global tropical cyclones--the lowest two-year total since satellite observations began in 1970. The 24-month period April 2010 - March 2012 had 141 global tropical storms, which is also a record low. That's quite a turnaround from 2004 - 2005, which saw near-record high levels of global tropical cyclone activity.

The Atlantic is quietThe disturbance near the Azores that developed on Saturday, Invest 92L, has weakened and is no longer being tracked by NHC. The models have backed off on their predictions of a potential subtropical storm developing over the Western Caribbean or waters near Florida this weekend, and none of the computer models is predicting tropical cyclone development in the Atlantic over the next seven days. If something did develop, the most likely location would be along an old frontal boundary between the Bahamas and Bermuda, early next week.

The hybrid low pressure system with both tropical and extratropical characteristics that formed Saturday over the far Eastern Atlantic, about 450 miles southwest of the southern Azores Islands (Invest 92L), has weakened considerably, and is unlikely to become Subtropical Storm Alberto. Wind shear has increased to a very high 25 - 40 knots over 92L today, causing a marked deterioration of the heavy thunderstorm activity. Also not helping is the fact 92L is over cold ocean waters of 68°F (20°C.) This is well below the 26°C usually needed for a tropical storm to form. Satellite estimates of 92L's winds were 35 mph at 7:45 am EDT Monday, according to NOAA/NESDIS. NHC estimated that 92L had top winds of 40 mph at 8 am EDT Monday, down 10 mph from Saturday's peak. Wind shear is expected to remain very high and water temperatures will cool as 92L moves northeast towards the Azores Islands on Tuesday and Wednesday, and the chances of the storm developing into a subtropical or tropical cyclone are near zero percent.

Eastern Pacific hurricane season beginsThe first tropical depression of the 2012 hurricane season has formed this morning in the Eastern Pacific, and it comes one day before the official May 15 start of the Eastern Pacific hurricane season. Tropical Depression One-E is located about 645 mi south of Manzanillo Mexico, and is headed west, away from any land areas. Wind shear is a low 5 - 10 knots, ocean temperatures are a warm 29°C, and TD One-E has a good chance of becoming the season's first tropical storm by Tuesday. It is unusual to get a tropical storm forming this early in the year in the Eastern Pacific; since record keeping began in 1949, there have only been two that have formed by May 15--Hurricane Alma of 1990, and an unnamed 1996 storm. TD One-E will not live for long--the storm is headed towards a region with high wind shear and cooler waters that should be able to destroy it late this week.

Only weak potential for an Atlantic system developing over the next weekThe models have backed off on their predictions of a potential subtropical storm developing over the Western Caribbean or waters near Florida this weekend, though it is possible we might see something develop along an old cold frontal boundary between the Bahamas and Bermuda. If such a storm did develop, it would likely move northeast out to sea.

Azores storm could become Subtropical Storm Alberto

An interesting and surprising hybrid low pressure system with both tropical and extratropical characteristics has formed over the far Eastern Atlantic, about 400 miles southwest of the southern Azores Islands. This low, designated Invest 92L by NHC today, has developed an impressive amount of heavy thunderstorm activity near its center, despite the fact that it is over cold ocean waters with temperatures of 66°F (19°C.) This is well below the 26°C usually needed for a tropical storm to form. However, there is quite cold air aloft, so the temperature difference between the surface the upper levels has been great enough to create sufficient instability for 92L to organize. Wind shear is a moderate 15 - 20 knots, and satellite estimates of 92L's winds were 63 mph at 1:45 pm EDT Saturday, according to NOAA/NESDIS. NHC estimated that 92L had top winds of 50 mph at 2 pm EDT Saturday.

NHC is giving 92L a 40% chance of developing into a named storm by Monday. They will be reluctant to name it Alberto unless the storm can maintain it's current level of heavy thunderstorm activity for at least 6 - 12 hours. The storm's heavy thunderstorms have weakened some during the afternoon, making it less likely NHC will be inclined to name it; the fact that 92L is over waters of 66°F (19°C) hurts its chances. The coldest waters I've seen a tropical storm form in were 19°C, during Tropical Storm Grace of 2009. Grace holds the record for being the farthest northeast forming tropical cyclone in the Atlantic basin. Like 92L, Grace also formed near the Azores Islands, but in early October. The coldest waters I've seen a hurricane form in were 22°C, for Hurricane Epsilon of 2005. Latest guidance from the computer models show 92L meandering to the south of the Azores through Monday, then beginning a slow motion towards the northeast by Tuesday.

The U.S. suffered its second billion-dollar weather disaster of 2012 on April 3, when a massive hailstorm and 21 tornadoes hit the Dallas/Fort Worth, Texas region, said insurance company Aon Benfield, in their latest monthly Global Catastrophe Recap Report. They put the damage at $1 billion. The tornado outbreak included one EF-3 twister, which hit Forney, Texas. A severe hailstorm during the outbreak hit the DFW airport, damaging over 100 airplanes, and forcing the temporary closure of the airport. The other billion-dollar weather disaster of 2012 was the March 2 - 3 tornado outbreak in the Midwest and Southeast. NOAA put the total cost of the tornadoes that killed 41 people in Kentucky, Indiana, Ohio, and Alabama during the outbreak at $1.5 billion. There were two EF-4 tornadoes, one which devastated Henryville, Indiana, and another that plowed through Crittenden, Kentucky. On average, the U.S. sees 3 - 4 billion-dollar weather disasters each year, with 1 - 2 of these being severe weather/tornado outbreaks. In 2011, we already had five billion-dollar weather-related disasters by the first week of May, so we are well behind last year's pace. NOAA's National Climatic Data Center logged a record fourteen billion-dollar weather disasters in 2011. There has been just one other billion-dollar disaster in the world this year, according to Aon Benfield--severe flooding in Australia's New South Wales and Victoria states in late February and early March that caused $1.58 billion in damage. A separate flooding episode in late January and early February came close, causing an additional $920 million in damage in Australia.

Video 1. Dramatic video of semi-trailers being tossed more than 100 feet in the air by the Lancaster, Texas tornado of April 3, 2012.

Canada and Midwest U.S. frost/freeze damage in the hundreds of millions of dollarsDamage to fruit trees in Ontario, Canada due to a series of frosts and freezes over the past six weeks will easily top $100 million dollars, said the Windsor Star this week. About 80% of the Ontario apple crop was wiped out. At the Ann Arbor Farmer's Market yesterday, I talked to a local apple grower who told me that her orchard in Southeast Lower Michigan had suffered at least a 90% loss of its apple crop. She said the story was similar for all the growers of apples, pears, peaches, nectarines, grapes, cherries, and plums in Michigan. "The only year that can compare was 1945," she told me, "and that year wasn't nearly as bad as 2012." Fruit crops in Pennsylvania and New York State have suffered heavy damage as well, and the total damage to agriculture from this year's freezes will likely be in the hundreds of millions of dollars. All of this damage occurred despite the fact that April temperatures across the region were above average. The culprit was the extraordinary "Summer in March" weather in mid-March 2012, which brought a week of 80°F-plus temperature to the region that triggered a record early bloom.

Figure 2. Morning satellite image of Eastern Pacific Invest 90E.

Hurricane season is comingIt's now mid-May, which means that hurricane season is about to start in the East Pacific. The official start of the East Pacific hurricane season is May 15, and the action is already starting to heat up. The first "Invest" of 2012 in the East Pacific, Invest 90E, is located about 700 miles south of Puerto Vallarta, Mexico, and is moving westward out to sea, posing no threat to any land areas. The European Center model predicts the possibility of another system getting organized in the East Pacific, closer to the coast of Mexico, during the period Wednesday - Friday (May 16 - 18.)

In the Atlantic, where hurricane season officially starts on June 1, the action may also be about to heat up. For the past several days, the GFS model has been consistently predicting the development of a subtropical storm in the Western Caribbean, or waters near Florida, sometime May 19 - May 21. The European Center model has not been on board with this, but has been predicting a very moist flow of tropical air will develop, bringing heavy rains to Florida May 19 - 20. So, it is possible we will see the Atlantic's first named storm occur in May this year, but the models are very unreliable this far out.

U.S. experiences warmest 12-month period on record

The past twelve months were the warmest twelve months in U.S. history, said NOAA's National Climatic Data Center (NCDC) on Tuesday, in their monthly "State of the Climate" report. Temperatures in the contiguous U.S. during May 2011 - April 2012 broke the previous record for warmest 12-month period, set November 1999 - October 2000, by 0.1°F. The past twelve months have featured America's 2nd warmest summer, 4th warmest winter, and warmest March on record. Twenty-two states were record warm for the 12-month period, and an additional nineteen states were top ten warm. NOAA said that the January - April 2012 period was also the warmest January - April period since record keeping began in 1895. The average temperature of 45.4°F during January - April 2012 was 5.4°F above the 20th century average for the period, and smashed the previous record set in 2006 by an unusually large margin--1.6°F.

Figure 1. The ten warmest 12-month periods in the contiguous U.S. since record keeping began in 1895. Image credit: NOAA/NCDC.

Figure 2. The average temperature of 45.4°F during January - April 2012 was the warmest on record: 5.4°F above the 20th century average for the period, and was 1.6°F above the previous record set in 2006. January - April temperatures have been rising at about 1.9°F per century since 1895. Image credit: NOAA/NCDC.

April 2012: 3rd warmest on recordApril 2012 was the third warmest April in the contiguous U.S. since record keeping began in 1895. Ten states had a top-ten warmest April, and no states were cooler than average. But what's really remarkable about April was that eight states--Illinois, Indiana, Kentucky, Michigan, Wisconsin, Ohio, Pennsylvania, and West Virginia--had average April temperatures cooler than their March temperatures, even though their April temperatures were still above the long-term average for the month. These statistics show just how remarkably warm March 2012 was. Most extreme was Illinois, where April 2012 temperatures ranked in the top 20% for warmest Aprils, yet were cooler than March 2012 temperatures.

Figure 3. Temperature rankings for April 2012 in the Contiguous U.S. Ten states had a top-ten warmest April, and no states were cooler than average. Image credit: NOAA/NCDC.

Most extreme January - April on recordNOAA's U.S. Climate Extremes Index (CEI), an index that tracks the highest 10 percent and lowest 10 percent of extremes in temperature, precipitation, and drought, was 42% during the January-April period, over twice the average value, and the greatest on record. Remarkably, 82% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically, and 68% had warm minimum temperatures in the top 10%, with records going back to 1910. The previous records were 56% (2000) and 57% (1992) for maximum and minimum temperatures, respectively. The percentage area of the U.S. experiencing top-10% drought conditions during January - April was 19%, which was the 17th greatest since 1910. Extremes in precipitation as computed by the CEI were near average for the January - April period.

Rare Japanese tornado kills 1, injures 48

A rare strong tornado ripped through Ibaraki Prefecture in eastern Japan 30 miles northeast of Tokyo on Sunday, killing a teenage boy, injuring 48 people, and damaging or destroying 890 buildings. The tornado carved a path of destruction 15 km long and 500 meters wide, said the Japan Meteorological Agency. The tornado was given a preliminary rating of F-2, with winds of 113 - 157 mph (Japan uses the traditional "F" scale to rate tornadoes, not the "EF" scale used in the U.S.) The tornado also damaged homes in a housing complex in Tsukuba where 20 people from seven families from Fukushima Prefecture had evacuated following the nuclear crisis at the Fukushima Daiichi power plant, caused by the earthquake and tsunami of March 2011. I bet those families are feeling disaster-prone!

Video 1. A rare tornado in Japan hits approximately 30 miles northeast of Tokyo on May 6, 2012.

Japan's tornado climatologyTornadoes are rare in Japan, due to the fact the nation is surrounded by ocean, which tends to stabilize the air. Between 1961 - 2010, an average of 15 tornadoes per year hit Japan, according to the Japan Meteorological Agency. Only four F-3 tornadoes have hit Japan. The most recent F-3 hit on November 7, 2006, in the Wakasa area of Saroma, Hokkaido. Nine people died and 26 were injured. Over 30 buildings, including a dwelling, warehouses and temporary structures were damaged or destroyed. No violent F-4 or F-5 tornadoes have been recorded in Japan, according the Japan Meteorological Agency, though other sources list a December, 1990 tornado as having been an F-4. Wunderground's weather historian Christopher C. Burt has more details in his latest post, Deadliest Tornadoes. Only one F-2 tornado hit Japan in both 2010 and 2011. A 1997 study published in the Journal of Climate found that Japanese tornadoes occurred most frequently in September and least frequently in March, and that typhoons were responsible for about 20% of all the tornadoes. A list of Asian tornado outbreaks maintained at Wikipedia lists the deadliest Japanese tornado as one on 6 September, 1881, which killed 16 people.

Photos from Climate Impacts Day

On Saturday, May 5, the activist group 350.org, founded by Bill McKibben, launched a new effort to "connect the dots between climate change and extreme weather." They declared May 5 Climate Impacts Day, and coordinated an impressive global effort of nearly 1,000 events in 100 countries to draw attention to the links between climate change and extreme weather. Their new climatedots.org website aims to get people involved to "protest, educate, document and volunteer along with thousands of people around the world to support the communities on the front lines of the climate crisis." Below are photos from some of the many events on Climate Impacts Day as archived on the climatedots.org website. It is remarkable to view the slide show on their web site and see the degree of global participation this event had; 350.org has created a dedicated and creative global climate movement that will be a major force to reckon with in the coming years.

Figure 1. Volunteers in the city of Salvador, Brazil, have connected the dots have and drawn people's attention to sea level rise and what it impacts in our life.

Figure 3. Activists hold a banner in front of a damaged coral reef in the vulnerable Marshall Islands. Rising temperatures and increased CO2 uptake are raising the acidity of the ocean, which bleaches and ultimately kills fragile coral reefs.

Figure 4. One thousand students in Bekaa, Lebanon make their dots into the wheels of a giant bicycle to raise awareness about the threat of air pollution, and to advocate for bike lanes.

Figure 5. In 2009, at 17,785 feet in Bolivia's Cordillera Oriental was the Chacaltaya Glacier. Before its unexpected melting, it was home to Bolivia's only ski resort and the first tow-rope ever to be built in South America. Today all that remains is a rocky mountain-top that only receives seasonal snowfall. Photo by Lauren Farnsworth.

Figure 6. Ausable Valley, NY, USA: Young people in New York understand the first-hand impacts of climate change. Hurricane Irene, the third five-hundred-year climate event in the last twelve months, devastated communities in the region and pummeled the beachfront with debris.

Connecting the dots between climate change and extreme weather

Connecting the dots between human-caused climate change and extreme weather events is fraught with difficulty and uncertainty. One the one hand, the underlying physics is clear--the huge amounts of heat-trapping gases like carbon dioxide humans have pumped into the atmosphere must be already causing significant changes to the weather. But the weather has huge natural variations on its own, without climate change. So, communicators of the links between climate change and extreme weather need to emphasize how climate change shifts the odds. We've loaded the dice towards some types of extreme weather events, by heating the atmosphere to add more heat and moisture. This can bring more extreme weather events like heat waves, heavy downpours, and intense droughts. What's more, the added heat and moisture can change atmospheric circulation patterns, causing meanders in the jet stream capable of bringing longer-lasting periods of extreme weather. As I wrote in my post this January, Where is the climate headed?, "The natural weather rhythms I've grown to used to during my 30 years as a meteorologist have become significantly disrupted over the past few years. Many of Earth's major atmospheric circulation patterns have seen significant shifts and unprecedented behavior; new patterns that were unknown have emerged, and extreme weather events were incredibly intense and numerous during 2010 - 2011. It boggles my mind that in 2011, the U.S. saw 14 - 17 billion-dollar weather disasters, three of which matched or exceeded some of the most iconic and destructive weather events in U.S. history."

Figure 1. Women who work on a tea farm in Assam, India hold up a dot in honor of Climate Impacts Day (May 5, 2012), to urge people to connect the dots between climate change and the threat to their livelihood. Chai is one of the most consumed beverages in India, but a prolonged dry spell and extreme heat has affected tea plantations in Assam and Bengal with production dropping by 60% as compared to the same period in 2011. Image credit: 350.org.

May 5: Climate Impacts DayOn Saturday, May 5 (Cinco de Mayo!), the activist group 350.org, founded by Bill McKibben, is launching a new effort to "connect the dots between climate change and extreme weather." They've declared May 5 Climate Impacts Day, and have coordinated an impressive global effort of nearly 1,000 events in 100 countries to draw attention to the links between climate change and extreme weather. Their new climatedots.org website aims to get people involved to "protest, educate, document and volunteer along with thousands of people around the world to support the communities on the front lines of the climate crisis." Some of the events planned for Saturday: firefighters in New Mexico will hold posters with dots in a forest ravaged by wildfires; divers in the Marshall Islands take a dot underwater to their dying coral reefs; climbers on glaciers in the Alps, Andes, and Sierras will unfurl dots on melting glaciers with the simple message: "Melting"; villagers in Northeastern Kenya will create dots to show how ongoing drought is killing their crops; in San Francisco, California, aerial artist Daniel Dancer and the Center for Biological Diversity will work with hundreds of people to form a giant, moving blue dot to represent the threat of sea level rise and ocean acidification; and city-dwellers in Rio de Janeiro hold dots where mudslides from unusually heavy rains wiped out part of their neighborhood. I think its a great way to draw attention to the links between climate change and extreme weather, since the mainstream media coverage of climate change has been almost nil the past few years. A report by Media Matters for America found out that nightly news coverage about climate change on the major networks decreased 72% between 2009 and 2011. On the Sunday shows, 97% of the stories mentioning climate change were about politics in Washington D.C. or on the campaign trail, not about extreme weather or recent scientific reports. You can check out what Climate Impacts Day events may be happening in your area at the climatedots.org website.

Figure 2. Front Street Bridge on the Susquehanna River in Vestal, NY, immediately following the flood of September 8, 2011. Image credit: USGS, New York. In my post, Tropical Storm Lee's flood in Binghamton: was global warming the final straw? I argue that during September 8, 2011 flood, the Susquehanna River rose twenty feet in 24 hours and topped the flood walls in Binghamton by 8.5 inches, so just a 6% reduction in the flood height would have led to no overtopping of the flood walls and a huge decrease in damage. Extra moisture in the air due to global warming could have easily contributed this 6% of extra flood height.

Also of interestAnti-coal activists, led by climate scientist Dr. James Hansen of NASA, are acting on Saturday to block Warren Buffett's coal trains in British Columbia from delivering coal to Pacific ports for shipment overseas. Dave Roberts of Grist explains how this may be an effective strategy to reduce coal use, in his post, "Fighting coal export terminals: It matters".

The creator of wunderground's new Climate Change Center, atmospheric scientist Angela Fritz, has a blog post on Friday's unveiling of the new Heartland Institute billboards linking mass murderers like Charles Manson and Osama Bin Laden to belief in global warming. In Heartland's description of the billboard campaign, they say, "The people who still believe in man-made global warming are mostly on the radical fringe of society. This is why the most prominent advocates of global warming aren't scientists. They are murderers, tyrants, and madmen." The Heartland Institute neglected to mention that the Pope and the Dalai Lama are prominent advocates of addressing the dangers of human-caused climate change.

New damage estimates released last month by NOAA now place the damage from 2011's Hurricane Irene at $15.8 billion, making the storm the 6th costliest hurricane and 10th costliest weather-related disaster in U.S. history. Irene hit North Carolina on August 27, 2011, as a Category 1 hurricane with 85 mph winds, and made landfalls the next day in New Jersey and New York City as a tropical storm. Most of the damage from Irene occurred because of the tremendous fresh water flooding the storm's rains brought to much of New England. Irene is now rated as the most expensive Category 1 hurricane to hit the U.S. The previous record was held by Hurricane Agnes of 1972, whose floods did $11.8 billion in damage in the Northeast. NOAA also announced that the name Irene had been retired from the list of active hurricane names. Irene was the only named retired in 2011, and was the 76th name to be retired since 1954. The name Irene was replaced with Irma, which is next scheduled be used in 2017.

Figure 1. True-color MODIS image of Hurricane Irene over North Carolina taken at 11:35 am EDT August 27, 2011. At the time, Irene was a Category 1 hurricane with 85 mph winds. Image credit: NASA.

Tornado hits France; unprecedented April heat in Europe

A rare EF-1 tornado with 73 - 112 mph winds (117 - 180 kph) hit Toulouse, France on Sunday, causing minor damage that included collapsed walls, uprooted trees, and cars moved out of place. The tornado touched down 15 - 20 km south of Toulouse in Southwest France at 7:10 pm local time, and baseball-sized hail (4 cm) also hit the region. According to the European Severe Weather Database (ESWD), this was the first tornado in France in 2012. French tornadoes are rare; there were just three tornadoes in the country in 2011. The European Severe Weather Database (ESWD) (as summarized by Wikipedia) lists 15 tornadoes for all of Europe so far in 2012. Most of the twisters (nine) were in Turkey. For comparison, an average of 495 tornadoes touched down in the U.S. during the period January - April over the years 2009 - 2011. A key reason for the lack of tornadoes in Europe is that the atmosphere is usually not unstable enough. Tornadoes require warm, moist, low-density air near the surface, and cold, dry, high-density air aloft to provide a lot of instability. The Baltic Sea and North Sea to the north of Europe moderate cold air flowing south from the pole, reducing the amount of instability over Europe.

Video 1. A rare French tornado kicks up dust near Toulouse, France on April 29, 2012.

Unprecedented April heat hits Central and Eastern EuropeA European heat wave of unparalleled intensity for so early in the year smashed all-time April heat records over much of Central and Eastern Europe on Saturday and Sunday. According to wunderground's weather historian Christopher C. Burt, and weather records researcher Maximiliano Herrera, new national April heat records were set in Belarus, Germany, Austria, Lithuania, Moldova, and Poland, and hundreds of stations in Germany, Austria, France, Italy, Hungary, Moldova, Romania, Poland, Belarus, Ukraine, Lithuania, Latvia, Czech Republic, Slovakia, and Russia recorded their hottest April temperatures on record. Moscow hit 28.6°C (84°F) on Sunday, the hottest April reading in the city since record keeping began 130 years ago. The culprit for the heat wave and French tornado is a large low pressure system off the coast of France whose counter-clockwise flow has been pumping hot air from the Sahara Desert northwards into Europe. The low is expected to continue to bring unusually hot weather to most of Central and Eastern Europe for the remainder of the week.